Do contact lenses protect the eye against toxic or hazardous chemical vapors or do they selectively absorb such chemicals?

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This answer comes from H. Dwight Cavanagh, M.D., The W. Maxwell Thomas Chair, professor and vice chairman
of ophthalmology at the University of Texas Southwestern Medical Center at Dallas.

Although it is widely believed
that contact lenses exacerbate the potential damage to the eye from chemical exposure, recent scientific studies indicate that
rigid (hard) and hydrogel (soft) contact lenses actually decrease the exposure of their wearer's eyes to toxic irritants in the
environment.

Perhaps the best study of this issue was published in the January 1992 edition of the Journal of the
Contact Lens Association of Ophthalmologists (CLAO Journal) by eye researchers who examined 128 cases of
occupational eye injuries in individuals who were wearing contact lenses at the time. This study confirmed and extended
previous findings that, overall, contact lenses partially protected and minimized--rather than worsened-- injuries.

Although the study also looked at a variety of injuries, including physical trauma, the data demonstrate that types of
contact lenses can provide important protection by decreasing the exposure of the eyes to volatile or toxic solvents in the air.

In another study of hard contact lenses, researchers simulated chemical splash accidents in laboratory animals. They
found that eyes fit with hard contact lenses experienced less corneal damage and that contact lenses essentially provided
protection against strong acids. In this study, animal's eyes were exposed to acetic acid, n-butylamine, or acetone.

A
similar study examined how well soft contact lenses absorb trichloroethylene (TCE) and xylene vapors. This study found that
high water-content contact lenses increased the concentration of the vapors within the lenses. But the researchers also found
that, although the uptake of the vapors by the contact lenses was considerable, the solvents were released primarily back into
the air, not the eye. In other words, wearing contact lenses did not increase exposure of the cornea to potential damage from
chemicals.

Image: Michigan State
University

SEVERE INJURY. Damage to eye was caused by a spill of a strong
alkali. The Occupational Safety and Health Administration estimates that 1,000 eye injuries occur daily in U.S. workplaces.

Sterile saline, which is a wetting agent used by many contact lens wearers, also appears to play a role in limiting the
damage certain chemicals and vapors can do to the eye. One of the most recent studies, conducted at the University of
Nebraska Medical Center, compared the absorption rate of saline solutions exposed directly to solvent vapors with the
absorption rate of saline used with contact lenses. The introduction of saline alone did not appear to further disperse the
chemicals or vapors over the eye's surface. And results from the test of the saline-contact lens combination further
demonstrated that eye damage was decreased; most of the vapors absorbed by the contact lenses were released back into the
air.

These observations have major relevance, especially for industrial and laboratory workers, who may be laboring
under traditional workplace restrictions that bar them from using contact lenses while on duty. Such restrictions appear to be
unnecessary in many instances.

But we must remember that the findings mentioned here do not apply to all chemicals and
solvents, so great care and knowledge of various chemicals and their effects continue to be necessary. Also, ophthalmologists
concur that additional safety precautions should be taken when working around concentrated chemicals that can cause severe
occular irritation or surface damage to the cornea; a pair of well-made safety goggles should always be used in occupations
that put employees at risk of exposure to severely toxic chemicals and vapors, such as concentrated acids or lye.

References:

H.D. Cavanagh, Contact Lenses in the Industrial Workplace: Are They Safe? The CLAO
Journal, 1992:18, 11.

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